import { Injectable } from '@angular/core';
import { Hero } from './hero';
import { HEROES } from './mock-heroes';
import { Observable, of } from 'rxjs';
import { MessageService } from './message.service';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { catchError, map, tap } from 'rxjs/operators';
const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json' })
};
// 注册提供商把这个服务提供给依赖注入系统
@Injectable({
  providedIn: 'root'
})
export class HeroService {
  // 看样子of()能将数据包装成Observable类(这个类与HttpClient.get返回相同)
  // getHeroes(): Observable<Hero[]> {
  //   this.messageService.add('HeroService: fetched heroes');
  //   return of(HEROES);
  // }
  getHeroes(): Observable<Hero[]> {
    return this.http.get<Hero[]>(this.heroesUrl)
      .pipe(
        tap(heroes => this.log('fetched heroes')),
        catchError(this.handleError('getHeroes', []))
      );
  }
  // getHero(id: number): Observable<Hero | undefined> {
  //   this.messageService.add(`HeroService: fetched hero id=${id}`);
  //   return of(HEROES.find(hero => hero.id === id));
  // }
  getHero(id: number): Observable<Hero> {
    const url = `${this.heroesUrl}/${id}`;
    return this.http.get<Hero>(url).pipe(
      tap(_ => this.log(`fetched hero id=${id}`)),
      catchError(this.handleError<Hero>(`getHero id=${id}`))
    );
  }
  // 注入messageService
  constructor(private http: HttpClient, private messageService: MessageService) { }
  private log(message: string) {
    this.messageService.add(`HeroService: ${message}`);
  }
  private heroesUrl = 'api/heroes';
  private handleError<T>(operation = 'operation', result?: T) {
    return (error: any): Observable<T> => { console.error(error); this.log(`${operation} failed: ${error.message}`); return of(result as T); };
  }

  updateHero(hero: Hero): Observable<any> {

    return this.http.put(this.heroesUrl, hero, httpOptions).pipe(
      tap(_ => this.log(`updated hero id=${hero.id}`)),
      catchError(this.handleError<any>('updateHero'))
    );
  }
  addHero(hero: Hero): Observable<Hero> {

    return this.http.post<Hero>(this.heroesUrl, hero, httpOptions).pipe(
      tap((hero: Hero) => this.log(`added hero w/ id=${hero.id}`)),
      catchError(this.handleError<Hero>('addHero'))
    );
  }
  deleteHero(hero: Hero | number): Observable<Hero> {
    const id = typeof hero === 'number' ? hero : hero.id;
    const url = `${this.heroesUrl}/${id}`;

    return this.http.delete<Hero>(url, httpOptions).pipe(
      tap(_ => this.log(`deleted hero id=${id}`)),
      catchError(this.handleError<Hero>('deleteHero'))
    );
  }
  searchHeroes(term: string): Observable<Hero[]> {
    if (!term.trim()) {
      return of([]);
    }
    return this.http.get<Hero[]>(`${this.heroesUrl}/?name=${term}`).pipe(
      tap(_ => this.log(`found heroes matching "${term}"`)),
      catchError(this.handleError<Hero[]>('searchHeroes', []))
    );
  }
}
